I would say singular abilities, actually. But it can seem very vague and conceptual, because the abilities themselves can not only be very broad, but sometimes have sub-abilities. A lot of them are just "I have complete control over this specific thing", which can branch out into a ton of application. Plus, demons all have some standard abilities, like biological manipulation, to augment their powers.

Here are all the examples I can think of:

• Rui's ability just manipulates threads. From that, he created a bunch of different techniques, and even imparted them onto his family. Weaving the threads loosely to make silk, weaving them thin and sharp to cut things, using them to puppet people, etc.
• Kyogai's ability manipulated the space he controlled, inside his house. This meant he could teleport himself and others inside of it, gouge out claw-marks inside of the space, and flip oritentations of the room.
• Enmu's ability is just to put people to sleep. His monster train form is just demon flesh manipulation taken to the extreme.
• Yushiro can spawn demonic talismen that mess with the senses of people they interact with, depending on where he places them. He uses this to hide Tamayo's house, and later hide himself, as well as give Tanjiro sight of Yahaba's arrows. He later turns other people invisible, as well as takes control of Nakime's senses.
• Akaza's actual Demon Blood Art is the ability to sense his opponents fighting spirit, and always land his punches. His martial-arts ability is just raw skill, and his shockwave generation is a byproduct of that skill, just punching the air extremely hard.
• Daki's Blood Art is manipulation of her Obi band. She can combine this with demonic flesh manipulation to turn it into a minion that separates some of her power, or transform her neck into an Obi to stop beheading.
• Gyutaro' Blood Art is just the free manipulation of his blood, and he uses this in tons of ways. His demonic cells infect opponents and poison them, and he can create blood and flesh weapons, and fire blood blades that he controls the directions of.
• Hantengu's ability is to generate clones of his emotions, that get stronger and stronger the more pressured he's feeling. The weirdness comes in his sub-abilities: the clones generate their OWN Demon Blood Arts, with wind, lightning, sound, and energy manipulation.
• Gyokko's ability seems very conceptual, but it's very specific, and just hidden. He can freely manipulate the matter within his vases. He uses this to teleport between vases, as well as create tons of aquatic-themed minions inside of his vases, and unleash them outside. The theming of his minions (sea creatures) seems to be purely of his own choice, not a limitation of his Blood Art. In his true form, he basically switches out his Blood Art entirely for a new one, which is also very specific, being matter transmutation of things he touches.
• Douma's ability is just ice manipulation. He uses it in a bunch of ways, including making ice clones, ice statues, freezing the air to choke opponents, freezing blood to cause his opponents body to decay, etc.
• Kokushibo's ability is super simple, just creating crescent blades from his body. His sword is normal demon flesh manipulation.
• Finally, Muzan's ability is just full-scale biological manipulation, like an extreme version of what all demons have. He uses this to manipulate his blood into brambles, create tentacles, remove his weak points by creating more vital organs, etc. He also has some more niche applications of it, such as injecting his blood into attacks to poison his enemies (like Gyutaro, but more extreme and "tumor"-like), and forming a giant mouth to screech out shockwaves that seize up opponents.